Traditional transportation modes via water, land, rail, and air revolutionized the movement and growth of our current culture. The adverse environmental, societal and economic impacts of these traditional modes of transportation, however, initiated a movement to find alternative modes of transportation that take advantage of the significant improvements in transportation technology so as to more efficiently move people and/or materials between locations. High-speed transportation systems utilizing rails or other structural guidance components have been contemplated as a solution to existing transportation challenges, while improving safety, decreasing the environmental impact of traditional modes of transportation, and reducing the overall time commuting between, for example, major metropolitan communities.
Particular high speed, high efficiency transportation systems utilize a low pressure environment in order to reduce drag on a vehicle at high operating speeds, thus providing the dual benefit of allowing greater speed potential and lowering the energy costs associated with overcoming drag forces. These transportation systems may use a near vacuum environment within a tubular structure. In embodiments, these tubular structures may comprise metal alloy (e.g., steel) and or composite materials, and may have a metal outer surface.
In embodiments, these tubular structures may be arranged in (e.g., partially or completely submerged) and/or over bodies water (e.g., fresh and/or salt water). Bodies of water include, for example, oceans, bays, rivers, sea channels (e.g., deep, narrow sea channels), and lakes, (e.g., deep lakes). For example, a submerged floating tunnel (SFT), also called a suspended tunnel or Archimedes bridge, is a tunnel that floats in water, supported (at least partially) by its buoyancy (for example, by employing the hydrostatic thrust, or Archimedes' principle). The tube may be placed under water, deep enough to avoid water traffic and weather, for example, at a depth of 20-50 m (60-150 ft). Cables, for example, anchored to the Earth and/or to pontoons at the surface prevent the SFT from floating to the surface or submerging, respectively. As should be understood, once arranged in position (e.g., under the surface of a body of salt water), the tubular structures are intended to remain in working position for extended periods of time (e.g., decades).
Submerged floating tunnels (or tubes) allow construction of a tunnel in deep water, where conventional bridges or tunnels are technically difficult or prohibitively expensive. SFTs are able to deal with seismic disturbances and weather events more easily (as they have some degree of freedom in regards to movement), and their structural performance may be independent of length (that is, the tube structure can be very long without compromising its stability and resistance).
When in these underwater salt environments, however, the tubular structures are susceptible to degradation (e.g., corrosion). Corrosion is the gradual destruction of materials (usually metals) by chemical and/or electrochemical reaction with their environment. In the most common use of the word, corrosion indicates electrochemical oxidation of metal in reaction with an oxidant such as oxygen or sulfur. Corrosion is a natural process, which converts a refined metal to a more chemically-stable form, such as its oxide, hydroxide, or sulfide. Corrosion engineering is the field dedicated to controlling and stopping corrosion. Rusting, which includes the formation of iron oxides, is a well-known example of electrochemical corrosion. This type of damage typically produces oxide(s) or salt(s) of the original metal, and results in a distinctive orange coloration. Corrosion can also occur in materials other than metals, such as ceramics or polymers, although in this context, the term “degradation” is more common. Corrosion degrades the useful properties of materials and structures including strength, appearance and permeability to liquids and gases.
The marine environment is one of the most brutally corrosive eco-systems in the world. Unprotected structures may erode prematurely, resulting in corrosion of structure and a weaker structure. Metallic surfaces are subject to corrosion by ions found in seawater and sea-air. This corrosion can result in structural failure, which often leads to a loss of profits, efficiency, and/or human life. Corrosion may be especially problematic at shallower depths and/or at the air/water interface.
The most common methods of preventing structural failure are: performance of frequent maintenance, and sacrificial treatments, such as, application and reapplication of anode coatings to metallic surfaces, installing an impressed current cathode protection system, or creating very thick metallic surfaces.
Additionally, surface treatments, such as epoxy-based coatings (which may be more long-lasting then the sacrificial treatments) may be applied to structures to retard corrosion. Great care, however, must be taken to ensure complete coverage, without gaps, cracks, or pinhole defects. Small defects, for example, can act as an “Achilles' heel,” allowing corrosion to penetrate the interior and causing extensive damage even while the outer protective layer remains apparently intact for a period of time.
Existing surface-treatment protection systems utilize a layer wrapped around the structure (e.g., steel and/or concrete pillars) that is designed to reduce corrosion on marine structures in environments where conditions may be too severe for paint systems, epoxies and other conventional forms of protection. The protection system seals out oxygen and water, effectively stopping corrosion on metal surfaces. The system also prevents spalling and corrosion of steel reinforcement in concrete piles. The system may encapsulate wharf piles, riser pipes and exposed piping in splash and intertidal zones. By sealing out the oxygen and water, the wrapping system effectively stops corrosion on metal surfaces, and also prevents loosening and corrosion of steel reinforcement in concrete piles. The marine piling wraps, (and jackets), coatings and petrolatum tapes are designed to protect assets for many years.
These methods of prevention, however, can often be costly and time consuming. Current practices do not utilize an efficient, cost-effective alternative to prevent seawater or sea air corrosion to metallic surfaces. Thus, while corrosion-prevention measures exist, there is a need in the art for further improved corrosion-prevention structures, systems, and methods for underwater environments.